The broad aims of the project are to investigate the molecular mechanisms underlying insulin action in mammalian cells. Apparent differences between normal and transformed cells in insulin sensitivity of intracellular protein degradation are used as the experimental model. Rates of proteolysis in transformed cells are much more sensitive to insulin inhibition, but this is not due to differences in the affinity of the insulin receptor nor to changes in the number of insulin receptors, and it is not due to a decreased rate of insulin degradation. The calculated number of insulin molecules that need bind per cell to achieve a 50% inhibition of proteolysis is over one order of magnitude less in transformed cells. We intend to broaden our approach to a variety of other normal and transformed lines, to look at the effect of other polypeptide hormones on intracellular proteolysis and to correlate insulin effects distal to the plasma membrane receptor with the regulation of protein degradation.